In late 1940 and 1950’s in East Germany, the government there spied on every facet of peoples lives after the war. The organization was known as the “Stasi” or secret police of East Germany.
From Wikipedia:
“One of its main tasks was spying on the population, mainly through a vast network of citizens turned informants and government agents. ”
They used phone tapping and photo surveillance to collect information on its citizens going about their daily business.